It is known that, on account of the rolling of the wheels on the runway, the lower part of the front gear of an aircraft is subjected to vibrations which are induced by the unbalance of the wheels, the unevenness of the runway or else through the landing gear entering torsional resonance, which is weakly damped.
Such vibrations have a frequency which is related to the rolling speed of the aircraft. Their amplitude depends on the dynamic characteristics of the front gear and the transmissibility of said vibrations to the remainder of the structure of the gear.
Even in the case where such vibrations are not significant enough to cause an accident, they are troublesome and dangerous and can cause interruptions to takeoff and/or damage, especially to the hardware of the electronic bays of the front part of the aircraft.
These vibrations, which occur even in a brand new aircraft through the resonance between the landing gear and the structure of the aircraft, cannot actually be assessed as long as the latter has not performed its first flight and the design of the front gear and of the structure of the aircraft has not been finalized.
Hence, to forestall the occurrence of such vibrations and/or to limit the effects thereof, it is indispensable to study them prior to the commissioning of each aircraft, so as to be able to parameterize the various devices of the latter accordingly.
Thus, in a known manner, to excite the front gear of an aircraft and study the resulting vibrations, the aircraft is raised up completely above the ground, by means of hydraulic rams. When the aircraft is raised, a static loading is applied to the wheels of the front gear with the aid of elastic cords, attached to the aircraft's towing hook, so as to limit the play between the various components of the front gear. The front gear is thereafter set into vibration by way of vibrating shakers disposed in contact with its wheels. The vibrations are recorded by means of sensors mounted on the structure of the aircraft.
However, in addition to the fact that the realization of such an excitation is lengthy and irksome to implement, the dynamic behavior of the front gear thus obtained remains very approximate and far from reality: the front gear, which does not rest on the ground, is completely unstressed, so that the subsequent adjusting of the various parameters of the aircraft is inaccurate.